[Conventional Reception Device: FIG. 8]
A conventional reception device will be described with reference to FIG. 8. FIG. 8 is a configuration block diagram of a conventional reception device.
As illustrated in FIG. 8, a conventional reception device includes a plurality of antennas 10, receivers 11 each connected to one of the antennas, analog digital converters (ADCs) 12 each connected to one of the receivers 11, amplitude/phase adjusters 13 each for adjusting the amplitude and the phase of signal data from one of the ADCs 12, an amplitude/phase controller 14 for outputting data for controlling the amplitude and the phase to the amplitude/phase adjusters 13, and a signal synthesizer 15 for combining the respective pieces of signal data the amplitude and the phase of which are controlled.
In the conventional reception device, the antennas 10 receive radio signals, and the receivers 11 output the radio signals to the ADCs 12 as analog signals. The ADCs 12 convert the analog signals into digital signals and output the digital signals to the amplitude/phase adjusters 13.
The amplitude/phase controller 14 outputs data (coefficient) for controlling the amplitude and the phase of each piece of the signal data from the ADCs 12 to the amplitude/phase adjusters 13.
The amplitude/phase adjusters 13 multiply each piece of the signal data from the ADCs 12 by the coefficient from the amplitude/phase controller 14 and outputs data of the reception signals the amplitude and the phase of which are controlled to the signal synthesizer 15.
The signal synthesizer 15 combines the signal data from the amplitude/phase adjusters 13 and outputs the result. The synthesized signal data output from the signal synthesizer 15 is subjected to signal processing by a device not illustrated.
In particular, in the reception device in FIG. 8, the amplitude and the phase of the plurality of antennas 10 are controlled by the amplitude/phase controller 14 in order to obtain a gain in a specific direction. As a result, achieved are functions of placing a directivity in a specific direction and reception of a target wave signal as well as controlling the amplitude and the phase to place a null point in a specific direction for elimination of interference waves in that direction.
[Conventional Antenna Radiation Pattern: FIG. 9]
An example of a radiation pattern in a case where a plurality of conventional antenna is used will be described with reference to FIG. 9. FIG. 9 is a diagram illustrating an example of a conventional antenna radiation pattern.
In an antenna radiation pattern as illustrated in FIG. 9, for example, null points (points between lobes) are narrow as compared with directivities gently forming lobes (with a shape of a protruding rounded tip).
A function of estimating an arrival direction of a signal is implemented by scanning the null points utilizing this characteristic.
[Conventional Interference Suppression Control]
Meanwhile in conventional interference suppression control, in order to separate interference waves and a target wave, reference signals of the interference waves are prepared by incorporation (stored) in advance or prepared by external input.
Alternatively, reference signals may be generated by using signal control technology such as a filter for extracting only interference components from characteristics of reception signals.
Then, by combining the reference signals of the interference waves with the reception signals in signal processing (removing the reference signals of the interference waves from the reception signals), interference wave components are suppressed.
Moreover, in recent years, technology of suppressing interference waves by generating a radiation pattern using a plurality of antennas and adjusting a null point to be directed in an arrival direction of an interference wave has also been in use.